Dissolution enhancers calcium carbonate

In the above equation the removal of C02, for example during photosynthesis, will enhance precipitation of CaC03. Likewise, the reverse reaction of respiration or decay of organic matter (for simplicity expressed as CH20) will result in dissolution of calcium carbonate (reaction 3). 

In soils, F can be found in four major fractions (1) dissolved in soil solution (2) sorbed to Al, Fe, and Mn oxides and hydroxides and carbonates (3) solid phases, such as fluorite and fluorophlogopite and (4) associated with organic compounds. The solubility of F in soil solution is variable and is affected by pH, speciation, adsorption and desorption reactions, and dissolution and precipitation reactions (Luther et al., 1996). Acidic conditions and low calcium carbonate content are favorable to F solubility and can therefore enhance both root uptake (Weinstein and Alscher-Herman, 1982) and migration to surface and ground water (Smith, 1983). These conditions can lead to human, plant, and animal health issues. Soils that do contain appreciable amounts of calcium carbonate and are neutral to slightly alkaline conditions can fix F as insoluble calcium fluoride (CaF2), and reduce its bioavailability and mobility (Kubota et al., 1982 Tracy et al., 1984 Reddy et al., 1993 Poulsen and Dudas, 1998). 

Calcium carbonate is the salt of choice because it contains the highest amount of elemental calcium and is the least expensive (see Table 88-5). The fraction of calcium absorbed is dose-limited, so maximum single doses of 600 mg or less of elemental calcium are recommended. Calcium carbonate tablets should be taken with meals to enhance absorption. Calcium citrate absorption is acid-independent and need not be administered with meals. Although tricalcium phosphate contains 39% calcium, nonabsorbable calcium-phosphorus complexes may limit overall calcium absorption compared to other products. This product may be required for up to 10% of seniors with hypophosphatemia that cannot be resolved with increased dietary intake. Disintegration and dissolution rates vary significantly between products and lots. Products with good disintegration and dissolution rates and lead contents of less than 1 mcg/day should be recommended. 

However, calcium carbonate budget calculations are strongly biased by inexact estimations of calcite production in the surface ocean and of the dissolution of pelagic biogenic calcite in the water column and in sediments above the calcite lysocline. In addition, the uncertainty is enhanced by the difficulty to estimate dissolved inorganic carbon release from sediments. 

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